|Publication number||US7462925 B2|
|Application number||US 10/987,468|
|Publication date||Dec 9, 2008|
|Filing date||Nov 12, 2004|
|Priority date||Nov 12, 2004|
|Also published as||US7755188, US7892888, US20060102993, US20070259482, US20090032923|
|Publication number||10987468, 987468, US 7462925 B2, US 7462925B2, US-B2-7462925, US7462925 B2, US7462925B2|
|Inventors||Chen Jung Tsai, Chih Wen Lin|
|Original Assignee||Macronix International Co., Ltd.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (19), Referenced by (6), Classifications (12), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
1. Field of the Invention
The present invention relates generally to multi-chip stacking fabrication methods and, more particularly, to fabrication of thin packages containing multi-chips.
2. Description of Related Art
Personal devices that require a large number of electronic components to be provided in a small volume are rapidly proliferating. A pocket-sized personal music player that includes a hard disk is only one example of such a device. Today's personal electronic devices require that more and more functionality must be provided in a relatively small space. Traditionally, this functionality was provided by multi-chip electronic devices fabricated by placing chips on a two-dimensional substrate such as a printed circuit board (PCB). As circuit density increased, methods were devised for stacking multiple chips, thereby trading a scarce resource of substrate area for space in a third dimension. Several prior-art structures for stacking multiple chips have been devised, but none has proven to be wholly satisfactory. The need to stack components typically requires fabricating a superstructure that supports the stacked components. This superstructure adds to the volume and weight, and therefore to the cost, of the component stack, thereby offsetting an advantage that may be gained by stacking. Some stacking structures make efficient use of space, but tend to be complicated and expensive to fabricate. Less complicated and expensive stacking structures may either fail to make efficient use of space and/or present problems in disposing of the heat generated by chips in a stack. Other stacking structures include delicate wires that may introduce reliability concerns. Still other stacking structures may introduce reliability concerns at the level of PCB interconnection.
A need thus exists in the prior art for a stacking structure that is efficient in its use of space while being easy to fabricate. A further need exists for a structure that achieves reliable interconnection with a PCB.
The present invention addresses these needs by providing a chip stacking structure wherein chips have via that extend through the chip, thereby obviating the need for external wires to form electrical connections either between chips or with external leads. The invention herein disclosed comprises a leadframe having a plurality of leads disposed at a periphery of the leadframe. According to an exemplary embodiment, each lead has a lead inner portion and a lead outer portion. The lead outer portion may connect reliably with a substrate such as a printed circuit board (PCB). Each lead inner portion comprises a first surface and a second surface. The invention further may comprise a first chip stack formed of at least one chip, each chip having an active surface, a back surface, a plurality of first bonding pads disposed on the active surface, and a plurality of first chip via. Each first bonding pad has a bonding wall, and each first chip via has insulating material covering an inner wall of the first chip via. The insulating material does not cover a bonding wall. Each of the plurality of first chip via extends from a first bonding pad through the chip to the back surface. This embodiment further comprises a second chip stack formed in a manner similar to the formation of the first chip stack. Chips in the second chip stack comprise active surfaces, back surfaces, second bonding pads, and second chip via. The second chip via have insulating material covering inner walls thereof. The second bonding pads have bonding walls that are not covered by insulating material. This embodiment of the chip stacking structure may be formed by filling each first chip via with conducting material that electrically connects each first bonding pad to the first surface of a lead inner portion. Similarly, each second chip via may be filled with conducting material, electrically connecting each second bonding pad to the second surface of a lead inner portion.
Another embodiment of the present invention comprises a chip stacking structure having a plurality of chip stacks, each chip stack including at least one chip. Each chip comprises an active surface, a corresponding back surface, and a plurality of bonding pads disposed on the active surface. Each bonding pad has a bonding wall. Each chip further comprises a plurality of chip via having inner walls and extending from the plurality of bonding pads through the chips to the back surfaces. Insulating material covers the inner walls but does not cover the bonding walls. The chip stacking structure further comprises a leadframe having a plurality of leads disposed at a periphery thereof with the plurality of leads having lead inner portions and lead outer portions. The lead inner portions have first surfaces and second surfaces. A first chip stack is positioned with a first active surface facing the first surfaces and with a first plurality of bonding pads aligned with and making contact with the lead inner portions. A second chip stack is positioned with a second active surface facing the second surfaces and with a second plurality of bonding pads aligned with and making contact with the lead inner portions. Conductive material electrically connects bonding walls in the first chip stack to the first surfaces. Similarly, conductive material electrically connects bonding walls in the second chip stack to the second surfaces.
The present invention further comprises a method of stacking semiconductor chips. An implementation of the method comprises providing a leadframe having a plurality of leads disposed at a periphery thereof, the plurality of leads having lead inner portions and lead outer portions. The lead inner portions have first surfaces, second surfaces, and lead via that extend through the lead inner portions. An aspect of this implementation of the method comprises providing a first chip stack comprising at least one chip having an active surface, a back surface, and a plurality of bonding pads on the active surface. Each chip further comprises a plurality of chip via extending from the plurality of bonding pads through the chip to the back surface. Another aspect of the method positions the first chip stack with a first active surface facing the first surfaces and with a first plurality of bonding pads aligned with and making contact with the inner portions. A second chip stack also is provided, the second ship stack likewise comprising at least one chip having an active surface and a back surface. Each chip in the second chip stack also has a plurality of bonding pads on the active surface and a plurality of chip via that extend from the plurality of bonding pads through the chip to the back surface. The method further comprises positioning the second chip stack with a second active surface of the second chip stack facing the second surfaces such that a second plurality of bonding pads of the second chip stack is aligned with and makes contact with the lead inner portions.
While the apparatus and method has or will be described for the sake of grammatical fluidity with functional explanations, it is to be expressly understood that the claims, unless expressly formulated under 35 U.S.C. 112, are not to be construed as necessarily limited in any way by the construction of “means” or “steps” limitations, but are to be accorded the full scope of the meaning and equivalents of the definition provided by the claims under the judicial doctrine of equivalents, and in the case where the claims are expressly formulated under 35 U.S.C. 112 are to be accorded full statutory equivalents under 35 U.S.C. 112.
Any feature or combination of features described herein are included within the scope of the present invention provided that the features included in any such combination are not mutually inconsistent as will be apparent from the context, this specification, and the knowledge of one skilled in the art. For purposes of summarizing the present invention, certain aspects, advantages and novel features of the present invention are described herein. Of course, it is to be understood that not necessarily all such aspects, advantages or features will be embodied in any particular embodiment of the present invention. Additional advantages and aspects of the present invention are apparent in the following detailed description and claims that follow.
Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same or similar reference numbers are used in the drawings and the description to refer to the same or like parts. It should be noted that the drawings are in simplified form and are not to precise scale. In reference to the disclosure herein, for purposes of convenience and clarity only, directional terms, such as, top, bottom, left, right, up, down, over, above, below, beneath, rear, and front, are used with respect to the accompanying drawings. Such directional terms should not be construed to limit the scope of the invention in any manner.
Although the disclosure herein refers to certain illustrated embodiments, it is to be understood that these embodiments are presented by way of example and not by way of limitation. The intent of the following detailed description, although discussing exemplary embodiments, is to be construed to cover all modifications, alternatives, and equivalents of the embodiments as may fall within the spirit and scope of the invention as defined by the appended claims. It is to be understood and appreciated that the process steps and structures described herein do not cover a complete process flow for the manufacture of stacking structures. The present invention may be practiced in conjunction with various integrated circuit fabrication techniques that are conventionally used in the art, and only so much of the commonly practiced process steps are included herein as are necessary to provide an understanding of the present invention.
Referring more particularly to the drawings,
An electrically conductive material such as solder may be used to fill the lead via 140 and first chip via 241 a. Solder may flow over first bonding pads 231 a thereby providing mechanical as well as electrical connection of the lead inner portions 130 to first bonding pads 231 a. According to another embodiment (not illustrated), chip 201 a has no via, and the first surface 110 of the lead inner portions 130 is secured to the active surface 211 a of chip 201 a by a solid or liquid adhesive.
In modified embodiments configured without lead via 140, alternative methods may be employed to create electrical contact between, for example, first surfaces 110 and first bonding pads 231 a. For example, a coating of conductive material (e.g., solder) may be provided on first surfaces 110 to enhance adhesion of a first chip via 241 a to a first surface 110. Moreover, convex conductive features (e.g., “bumps”) may be formed on first surfaces 110 in order to enhance alignment and adhesion of first chip via 241 a to first surfaces 110.
The placement of chip 202 b relative to chip 202 a is similar to the placement of chip 201 b relative to chip 202 a. Chip 202 b has an active surface 212 b and a corresponding back surface 222 b. A plurality of bonding pads 232 b are disposed on the active surface 212 b, each bonding pad 232 b being connected to a chip via 242 b. The chip via 242 b extend from the bonding pads 232 b to the back surface 222 b. The active surface 212 b of chip 202 b faces and contacts the back surface 222 a (
It should be clear from the examples presented herein that the direction in which chips face, i.e. up or down, is not constrained by present description of the invention. Rather, the facing direction of chips can be chosen according to aspects of a particular design or application.
The structure illustrated in
In view of the foregoing, it will be understood by those skilled in the art that the methods of the present invention can facilitate formation of efficient stacking structures for integrated circuits. The above-described embodiments have been provided by way of example, and the present invention is not limited to these examples. Multiple variations and modification to the disclosed embodiments will occur, to the extent not mutually exclusive, to those skilled in the art upon consideration of the foregoing description. For example, the embodiments illustrated in
Additionally, other combinations, omissions, substitutions and modifications will be apparent to the skilled artisan in view of the disclosure herein. Accordingly, the present invention is not intended to be limited by the disclosed embodiments, but is to be defined by reference to the appended claims.
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|U.S. Classification||257/676, 257/E23.052, 257/686, 257/E23.04, 257/E23.031|
|International Classification||H01L23/02, H01L23/495|
|Cooperative Classification||H01L23/49575, H01L23/481, H01L2224/16, H01L2924/01057|
|Nov 12, 2004||AS||Assignment|
Owner name: MACRONIX INTERNATIONAL CO., LTD., CHINA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:TSAI, CHEN JUNG;LIN, CHIH WEN;REEL/FRAME:015992/0864
Effective date: 20041028
|Mar 19, 2012||FPAY||Fee payment|
Year of fee payment: 4
|Mar 16, 2016||FPAY||Fee payment|
Year of fee payment: 8